The present invention relates generally to valves of the straight compression type, which are designed to be used without washers, but which, under certain conditions, may be used with the addition of a washer.
Prior to about 1960, the use of plastics or plastic materials in the construction of valves was virtually unkown, and valves, faucets, and the like, were made of metals or metallic materials, the surfaces of which had to be ground to achieve even a fairly serviceable seal.
In order to improve the seal, it was customary to use washers made of rubber, plastic, or other non-metallic material, but such washers, due to wear or distortion or for other reasons, required frequent replacement.
Examples of the use of such washers are found in the Higgins et al U.S. Pat. No. 1,886,677 and the Weaver U.S. Pat. No. 1,097,492.
In the Higgins et al U.S. Pat. No. 1,886,677, a valve structure is disclosed, in which a "stepped" opening connects the inlet and outlet openings of the valve, said opening comprising an aperture 18 which opens into an inlet passage 12 and a larger aperture 20 opening into the outlet passage 14. A ledge 22 is provided between these apertures, upon which the valve unit is adapted to seat. A valve stem 26 is threaded into the body 10 of the valve and has secured to the lower extremity thereof, by means of a screw 28, a packing washer 30.
When the valve stem is forced downwardly, the packing washer is forced to seat upon the ledge or seat 22. The head of the screw 28 is of a diameter and thickness just sufficient to completely fill the aperture 18 when the packing washer 30 is seated on the ledge 22.
It is stated, in the aforesaid patent, that the pressure in the water supply line is entirely taken up before reaching the washer 30 by virtue of the fact that the head of the screw 28 completely closes the opening 18. It is further stated that inasmuch as practically no pressure reaches the valve seat 22, there is no necessity for grinding this seat to enable the valve, when seated, to completely close the passage and prevent leakage.
The statement that the head of the screw 28 completely closes the aperture 18 is tantamount to stating that in order to obtain a good seal, it is required that the head of the screw be made to precise or exact dimensions in order to obtain a shutoff, and that the omission of the screw will not provide a proper shutoff.
Moreover, since, as stated in the patent, the washer 30 is made of leather, rubber, or some other resilient or yieldable material, and the seat 22 is an unground surface, it must be concluded that this washer is necessary, and that the valve stem, in the absence of the washer, will not prevent leakage of the valve.
In the Weaver U.S. Pat. No. 1,097,492, a faucet is disclosed, in which the faucet casing 11 has an inlet end 12 and an outlet end 13, and a valve seat 14 is formed between the inlet and outlet. The valve stem 16 has a head 17, to which a washer 20 is secured by a screw 21. The washer 20 is adapted to be seated on the seat 14.
It is not apparent, in the Weaver patent, that a leak-proof seal can be obtained without the use of the Washer 20, which is obviously made of a soft, non-metallic material.
In the Greene et al U.S. Pat. No. 3,386,700, an example of a faucet type valve is shown, made substantially in its entirety of resilient plastic material, in which the valve stem is provided with a tapered cone or plug portion which is designed to coact with a conical seat on the body of the valve to effect closure of the valve.
Due to the inclination of the tapered cone or plug and the conical seat, it was found that it was difficult to effect a leak-proof, positive shutoff of the valve.
Moreover, due to the inclination of the tapered cone, and the absence of a flat surface on the lower end of the cone, it was found to be impossible to utilize a washer in conjunction with the stem of the valve.